The overall goal of this research is to investigate the regulation of pituitary and adrenal function in the mammalian fetus and neonate. This includes determination of physiologic control mechanisms during development in normal and in chronically compromised detuses, the study of pituitary and adrenal regulation in the normal and premature neonate, and finally, investigation of factors affecting the increased fetal adrenal responsiveness to ACTH that occurs late in gestation. The animal model chosen for study is the chronically cannulated ovine fetus. This model allows study of fetal pituitary and adrenal physiology in the absence of complications induced by the presence of anesthesia and non-specific stress, both of which are inherent in experiments on acutely prepared animals. This preparation allows delivery of viable neonates so studies can be conducted before and after birth in the same animals to determine what changes in the ability to regulate pituitary and adrenal function occur as a consequence of parturition. These studies are necessary for a more complete understanding of the ontogeny of the control of endocrine factors vitally important in the maintenance of fetal and neonatal homeostasis under normal and pathologic circumstances. Results of our efforts to elucidate, at different stages of development, fundamental concepts of regulation of hormone systems important in the control of metabolism, blood pressure and blood volume may provide pertinent for clinical therapy in the premature infant and/or in the term infant in distress.